Incrementing VERSION to 73.0.3683.15

TBR=benmason@chromium.org

Change-Id: I9e644d18b44369e236a9a534e77c6a439bfc6c1a
Reviewed-on: https://chromium-review.googlesource.com/c/1449375
Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/branch-heads/3683@{#103}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
1 file changed